Project Summary The overarching hypothesis of this Program is that the airway epithelium serves as a central coordinator of the responses to respiratory virus infection, and that sensitization to aeroallergens and intrinsic differences in airway epithelial cells (AECs) between asthmatic and healthy individuals is the critical link between exposure and the development of dysfunctional airway responses in asthma. In Project 1, we will investigate the role of AEC-derived TGF? in regulating airway ECM composition, including regulation of VCAN and HA accumulation and their degradation products in the airway ECM leading to increased adhesion and activation of inflammatory leukocytes. Based upon observations by our group and others, and additional preliminary data presented in Project 1, we hypothesize that viral infection with RSV or HRV, and allergen exposure with the common aeroallergens cockroach antigen (CRA) or house dust mite (HDM), of AECs from asthmatic as compared to healthy children induce human lung fibroblasts (HLFs) to produce an airway ECM enriched with VCAN, HA and their degradation products, leading to increased adhesion and activation of inflammatory leukocytes. We will test this global hypothesis and investigate mechanisms responsible for airway matrix dysregulation in asthma, and the resulting increased adhesion and activation of leukocytes. Using human asthmatic AEC and AEC/HLF co-cultures we will determine the effects of viral infection and aeroallergen exposure with CRA and HDM, on asthmatic AEC regulation of HLF ECM production and composition. Furthermore, we will determine the effects of asthmatic AEC infection by respiratory viruses and exposure to CRA or HDM antigen on leukocyte adhesion to and activation by ECM produced by HLF. Finally, using a murine model of viral-triggered asthma we will determine the role of epithelium in regulating cellular responses during viral infection and exacerbation.